Henos Thoughts for the Westex Il] Meeting.
Jet Propulsion Leboratory, April 21, 1959

Dear Colleague:

At the Westex II meeting it was mentioned that the Jet Fropulsica
Laboratory had besn assigned the technical supervision of the Atias-Vega
recket. The Vega is the next generation of deep space vehicles and will
be used fox a variety of purpeses. The first stage is a modified
Atlas ICBM buil% by Convair Astronautics Corporation, The second stage
is a GE 05 engine or modified Vanguard first stage. The thi:d stage is
now being developed at the Jet Propulsion Leboratory amd is usually
referred to as the GK becaugze it is designed to produce 6000 pounds
thrust.

The first Vega Launching will take a trajectory out pasi: the Moon.
This will ccecur in the middle of 1960, The second Vega will be sent in
the direction of Mars hopefully missing it by no more than a iaiilion
miles. This launching will take place in late September of 1960 and the
probe will arrive in the neighborhood of Mars approximately 15 days
later. The third Vega launching atiempt will take place in January of
1961 amd the probe will be sent in the direction of Venus. ‘The trip
will. take approximately 90 days. This is the way the proeran shapes up
now, It may be necessary to change it.

The gross payloads for each of these shots are?

lst 1GG Ibs hioon miss
2nd $00 lbs Mars miss
3rd =: BOO Tbs Venus misg

The gross payload incindes the power supply, guidance, csommnicati.o
systems, etc., leaving considerably less for scientific instruments, The
current astimate of the scientific package weights are:

lz: 100 + Ibs Moon
23 20 ibs | Mars
3: 80+ Ibs Venus

Oowieusly, the Mars mission poses the mcst serious techiical
problems, It also presents an opportunity for the United States to
regain some prestige in the space field.

The Soviet Union already has an ICBM rocket developed for deep
espace work and it is quite likely that they will again demonstrate their
superiority next June when Venus and Earth approach opposition.
 

4 the momeric, the first priority exporiment on the Nary prone 1s
an infre-red optical systen. Hopefvliy, we can obtain new information
that will prove useful in planning subsequent Mars missions, For

example , 2 10 inch reflector 10° miles from Nara has four tines the
yadiation collecting power of the 200 inch telescope when ‘ers is av
opposition to the Earth, We believe a 20 inch reflector is feasible
for a ‘ers probe and that the probe may come within a half million
miles. This would provide a radiation collecting factor of Sh better
nan what Sinton had with the Palomar telescope,

Sinten observed Mars in the 3-) Qi oregion. Calvin suggests thai,
there are many organie compounds which would show the 3.43 p dip and
that some more characteristic spectrum should be Looked for. He has
taken a reflection spectrum of milled nylon, The peptide Linkage shews
a refisctions peak at wave number 1532. fnother reflecticn peak occurs
at about 1611. (This is in the neighborhood of 6 py.)

I have made som calculations on the gicunt of energy received from
the entire Mars planet ab a distance of 10° Kkiiometers, The total
radlation consists of two parts, the Sun's radiation reflested trom

Mars, and the omitted radiation. Mars is assumed to radiate approxinately

like @ black body at 250° K, The albedo is taken to be 0.1 ies s

ce (A) = reflected power in watts per micron at wavelength A
eed

Ep (A) ® emitted power in watts per micron.

Aa & area of reflector in em.* ~ 2000 am.*

 

Ey (3eh a) = 6.1 x 10° ag watts m4
Ey (5.72) = 0.98 x 10720 ay watts pot
Ep (7m) = 0,86 x 10°29 2. watts al

Bp (6.5) = 0.65 x 1079 4; watts p~

 

nn

» (6m) = 1.75 x 10? Ag watts pvt

 

Mars is net a black body, but a gray Dody. It seems Likely that
Calvin's refisction spikes will show up as spectrum dips,

iiere IT Laboratory wors is badly needed. 25 showld not be diffieuls
to gst such work financed. Preliminary investigation indicaios that
there is no clagsified work of this nature.
Can we get the radiation into a spectresceps aperture? if we can,
deteetion does not appear to be a problem, If the light losses ara not
high, then as little as a 30th of the area of Mare can be scaaned.

Pb Se may be a suitable detector in the 6y vegion,. At low tmperae
tures it has a sensitivity of about LO™ 1 watte and a time constant of
10"? seconds.

fn infraered telescope wovld also be useful on a Venus probes
Temperatures of the Cytherian atmosphere are currently estimated from
radiation in the 8 ~ region and the 10-13 p region.

What ideas do you have for the Mars and Venus migsions? There ig
not much time and we must make our decisions soccie

Locking forward to seeing you,

R. W. Davies